That will depend on your credentials. At a normal, middle class neighborhood private school you can expect something in the $10,000 to $12,000 pesos range, with full benefits. At the top tier colegios you can earn up to $25,000 and a salary of $30,000 is not unheard of, but you will earn every peso of it, both in terms of what is expected of you, and what you will have to put up with. Ironically, you will be treated far better by both students and parents in the lower paying schools than in the elite ones.